1. Field of the Invention
The present invention relates, generally to medical devices. More particularly, the invention relates to expandable implantable devices, particularly vaso-occlusion devices used in radiology and embolotherapy. Specifically the invention relates to devices and methods for installing vaso-occlusion devices.
2. Background Information
In embolotherapy, it is often desirable to occlude blood flow in a section of vasculature for purposes such as controlling internal bleeding, stopping blood supply to tumors, and relieving vessel-wall pressure in a region of a vessel aneurysm. Several devices and methods have been developed for such purposes, many of which are described in U.S. Pat. No. 4,994,069. Each has significant drawbacks, but the helical wire coils seem to have found the most favor. One difficulty with helical wire coils is in pushing, and, if necessary, pulling them through the catheter. The wire coil is dimensioned to engage the walls of a blood vessel and can be relatively stiff and difficult to advance through a catheter, especially if the blood vessel has a tortuous path. U.S. Pat. Nos. 5, 226,911 and 5,250,071 describe mechanical devices that attach and detach to the coils to provide more positive pushing, pulling and positioning capability, but they are relatively complex.
The device of U.S. Pat. No. 4,994,069 (the '069 patent) overcomes many of the problems with wire coils. It provides a smaller coiled wire that when tensioned has a linear configuration allowing it to be advanced through a catheter to the desired site. When the wire exits the catheter, it relaxes and takes a random convoluted shape to form a space-filling mass lodged in the vessel at the site of release. However, because the final shape of the relaxed coil in the blood vessel is random, the precise location and specific length the device occupies in the vessel cannot be guaranteed. Straightening the long coiled wire and inserting it into a catheter can also be problematic.
A device which overcomes the problems associated with the device of the '069 patent is described in a pending U.S. patent application, Ser. No. 08/608,110, titled Self-Expanding Vascular Occlusion Device, filed on Feb. 28, 1996. The above application is hereby incorporated by reference.
The present invention provides a device and method of loading an expandable vascular occlusion device of the Ser. No. 08/608,110 application into a catheter for insertion into vasculature of a patient. A device and method of the present invention may also be useful to load other expandable devices into catheters, including the device of the '069 patent and other wire coils.
Expandable implantable devices which could benefit from the present invention include any device which has a stretched condition characterized by an elongated shape of smaller diameter and a relaxed condition characterized by a shorter shape of larger diameter. In the past, such expandable devices have been stored in their stretched condition inside a tube. The device may experience creep during long term storage in that condition. Such creep may prevent the device from fully returning to the intended shape in its relaxed condition. This is especially a problem with devices using plastic material in their springy components. Another potential problem with devices stored in a tubes is that such storage prevents a physician or anyone else from examining the device before it is installed. The storage tube may have a label with a picture or illustration of the device and a description. There is always a potential for mislabeling the tube, or even for the device to be missing from the tube.
An introducer of the present invention allows an expandable implantable device to be attached to the tip of the introducer, but the device remains in its relaxed condition outside of the introducer. The device is not subject to creep during long term storage in this condition, and the device can be examined to verify the device is appropriate for the intended use before the package containing the device and introducer is opened.
It is an object of the present invention to provide an introducer for use with an expandable implantable device which holds the device in its relaxed condition outside of the introducer.
It is another object of the present invention to provide an introducer for use with an expandable implantable device which pulls the device into the introducer, moving it into its stretched condition as it does so.
It is yet another object of the invention to provide an introducer for use with an expandable implantable device which places the device in its stretched condition in a predetermined position within the introducer.